Automatic telephone system



Dec. 25,1928.

R. F. scum AUTOMATIC TELEPHONE SYSTEI Filed Dec. 1, 1926 2 Shoots-Sheet 1 at: b E:

Dec. 25,192

' R. F. GOULD AUTOIIATIC TELEPHONE SYSTEM Filed Dec. 1, 1926 Patented Dec. 25,- 1928 UNITED: STATES PATENT OFFICE.

BOY I. GOULD, OFCHICAGO, ILLINOIS, ASSIGNOR T0 RESERVE HOLDING COMPANY,

OF CHICAGO, ILLINOIS, A CORPORATION OF DELAWARE.

AUTOMATIC TELEPHONE SYSTEM.

Application filed December 1, 1926. Serial No. 151,907.

This invention relates to telephone systems in general, but more particularly to the equipment in a manual toll switching center for completing toll calls for a plurality of private automatic exchanges, for completing connections with train dispatchers lines, and for manually intercepting and completing calls for private automatic exchange subscribers lines which are in trouble.

One feature of the invention relates to special equipment at the toll switching center for enabling the operator to give manual service to private automatic exchange subscribers whose lines are in trouble to such an extent that the subscribers are unable to dial over their lines, but are able, however, to talk over their lines when connections are completed thereto.

The various features of the invention will be described in detail in the following specification in connection with the explanation of theoperation of the various circuits which are described with the aid of the accompany ing drawings.

Referring now to the drawings, Fig. 3 11- lustrates diagrammatically the trunking arrangement in connection with the toll switching center, while Figs. 1 and 2, when Fig. 2 is placed to the right of Fig. 1, illustrate the circuits and apparatus.

Referring to the drawings, Fig. 3 represents the private telephone system of a railroad center in which the toll lines marked TL represent long lines to various points in the system, the uppermost P. A. X. represents the private automatic exchange in the general oilices of the railroad company, the lower P. A. X. represents the private automatic exchange in the railroad work shop or round house, while the lowermost trunk line TR represents a train dispatchers trunk circuit. Two-way trunks TC from the P. A. X.s, toll trunks TL, and train dispatchers trunks TR terminate in jacks at the toll switching center which is preferably located in the same building as the general oflices of the railroad company. The toll switching center, designated TSC, comprises a toll operators position which is primarilyused for interconnecting toll lines or for connecting private automatic subscribers lines with toll lines or dispatchers trunks.

Special trunks are provided between the P. A. X.s and the toll switching center for enabling the operator at the. switching center to intercept and complete calls for P. A. X. subscribers lines which are out of order. Such trunks are commonly known as hospital trunks and would be connected to the lines of important subscribers, such as the railroad traffic manager, during thetime such lines are out of order. Direct automatic trunks (not shown) extend between the P. A. X.s from the ninth levelof the selector connector switches in oneP. A. X. to incoming connector switches in the other P. A. X.

Referring toFig. 1, station A, shown in the upper left-hand corner, is an automatic subscribers line and station equipment. The station A consists of a. calling device and .the usual instrumentalities to enable a subscriber to carry on conversation.

The line of station A terminates at the private automatic exchange in the main distributing frame MDF from which point it extends byway of ajumper. and the usual line protecting apparatus (not shown) to its lineswitch LS and to contacts in the banks of the selector connectors.

The lineswitch LS is of the usual nonrestoring or rotary type of lineswitch while the selector connectors, (not shown) are of the well known Strowger type of switch.

A hospital trunk plug HTP is shown just to the right of the main distributing frame MDF. This plug and the associated trunk are for use in case a. subscribers line is out of order. The plug HTP is so designed that hospital trunk equipment HT and HT and jacks J and J, respectively. The hospital trunk HT is designed especially for intercepting calls from a subscribers line which is out of order, while the hospital trunk HT is provided with means for intercepting calls to subscribers lines.

The cord circuit CC at the toll switching center is a double plug ended cord circuit of the universal type. c In the cord circuit there i is provided two ringing keys, two dialing keys, a listening key, and a pair of relays which are used for supervisory purposes on toll lines.

Either plug of the cord circuit is adaptable to be inserted into either of the jacks of the hospital trunks HT and HT. The cord circuit is also adapted for use with two way trunks connecting the toll switching center with the private automatic exchanges, for use in connecting the switching center with train dispatchers lines and is also used for connecting long distance toll lines.

The operators headset 0 shown directly above the cordcircuit is provided with a calling device CD and the usual instrumentalt ties for permitting her to converse with either the calling or called subscriber.

In the upper half of Fig. 2 there is shown a two-way trunk circuit TC terminating in one end at the toll switching center in the jack J and in the other end at the private automatic exchange in the lineswitch LS and selector connector bank contacts. The trunk circuit TC and similar trunk circuits are used for extending calls to and from the toll switching center. The lineswitch LS and selector connectors are located in the private automatic exchange and are of the same type as those described in connection with Fig. 1. The talking conductors extending from the selector connector banks to the line conductors of the trunk TC are, however, reversed for supervisory purposes.

In the lower half of Fig. 2 is shown a train dispatcher-s circuit TR terminating in one end at the toll switching center in the jack .1 and in the other hand in a train dispatehers station DIS. This trunk continues through the dispatchers station to a plurality of waystations lVS. The train dispatchers trunk and similar trunks are adapted by the aid of the cord circuit CC, to be connected to other dispatchers trunks or may be connected to toll trunks or to any of the private automatic exchange subscribers lines.

W'ith this general description of the drawings in mind, the operation of the circuits may now be explained in detail. For this purpose, it will be assumed that the subscriber at substation A is the railroad traific manager and that it becomes necessary for him to be connected with the train dispatehers trunk TR. Responsive to the removal of the re ceiver by the subscriber at the substation A, a circuit is closed for the line relay (not shown) of the lineswitch LS as follows: from ground on the lower armature of the cut-off relay of the lineswitch LS, conductor 9, protector spring 7 and its working contact, conductor 1, station A, conductor 2, line protcctor spring 6 and its working contact, conductor 10, and through the winding of the line relay to battery. The line relay of the lineswitch energizes over the above traced circuit and causes the lineswitch LS to hunt for an idle selector connector (not shown). After the lineswitch LS seizes an idle selector connector the calling station A dials the digit 0. Responsive to the digit dialed by the calling station, the selector connector is directively raised to its tenth level and automatically hunts for an idle trunk extending to the toll switching center TSC. hen an idle trunk circuit, such as TC, is seized by the selcctor connector the wipers of the selector connector come to rest on bank contacts, such as contacts 117, 118, and 110 shown in Fi The cut-oft relay of the associated lineswitch LS and the switching relay of the selector connector energize in series over conductor 120 and connector bank contact 118 in a well known manner. By the operation of the switching relay in the connector, ringing current is applied to the trunk circuit TC thereby causing the operation of ring-up relay 103. Ring-up relay 103, upon energizing, closes a circuit for lighting the lamp L It may well be mentioned at this time that the ringup relay 103, when operated, mechanically locks itself in an operated position until the cut-off relay 10:? is energized. A relay combination and mechanically locking arrange ment of this type are disclosed in the Patent 1,007,?14, issued Oct. 31, 1911 of John Erickson.

The operator at the switchboard, perceiving the lighted condition of the lamp L". inserts the plug P or P into the jack J of the trunk circuit TC. Responsive to the insertion of the plug P into the jack J a circuit is closed for energizing the cut-oil relay 102. Relay 102, upon energizing, closes a circuit for energizing the sleeve relay 101 at arma ture 108; opens the circuit of the ring'up relay 103 at armature 110; and releases the mechanically locking mechanism of the ringup relay 103 thereby allowing said relay to deenergize and extinguish the lamp if. The circuit for energizing relay 101 may he traced as follows: from ground by way of armature 108 and its working contact, upper winding of: relay 101, sleeve conductor and sleeve of jack J sleeve of plug 1 to a point 68 where the circuit divides, one branch em tending through the resistance 50 to battery. while the other ln'anch extends through spring 4;? and its resting contact of ring key RK, resting contact of armature 18 and said armature to supervisory. lamp SL and but tery. Another branch may also be traced through the resistance (35) to battery. It may well ben'ientioned at this time that the supervisory lamp SL is notlightcd over this elrrui t because of the high resistance of the upper winding of relay 101. Sleeve relay 101, upon energizing over the above traced circuit, closes a bridge across the conductors 111 and 112 at armature 1013 and its working contact. The bridge across the trunk conductors 111 and 112 includes the right-hand windings ofthe repeatin coil and the polarized relay 100 in series. Ty the closure of this bridge a relay operation in the connector takes place which cuts off the ringing current thereby connecting the line conductors 01" the calling After the insertion of the plug P into the jack J the operator at the switchboard will operate the listening key LK and converse with the calling party. By the operation of the listening key LK', the operators head set 0 is connected directly across the trunk.

The operator, upon ascertaining that it is desirable to connect the calling party with a train dispatchers trunk such as TR, inserts the plug P into the jack J of the desired train dispatchers trunk TR. Responsive to the insertion of the plug P into thejack J 3 of the train dispatchers trunk circuit TR, a circuit is closed for energizing sleeve relay 132 as follows: from ground by way oi the high resistance winding of relay 132, sleeve of jack J sleeve of plug P, resting contact of spring 58 and said spring of ringing key RK tothe supervisory lamp SL and battery. A branch of the above circuit also extends through resistance 60 to battery. Relay 132, upon energizing at armature 13%. opens the circuit for the lamp L, at arinature 135 and its working contact prepares a circuit for operating the supervisory lamp SL in case the dispatcher wishes to recall the operator; and at armature 136 and its working contact closes the speaking leads through right-hand windings of the repeating coil to the train dispatcher. It will be noted that no means has been provided for signalling the dispatcher because none is needed as the dispatchers head-set is permanently con nected across the trunk conductors 130 and 132. The calling party and the dispatcher may now converse with each other as do sired.

After conversation the calling subscriber, upon replacing his receiver, causes the release of his lineswitch and connector in a well known manner. By the release of the connector the cut-ofi relay in the lineswitch LS releases and connects battery and ground to conductors 111 and 112, respectively, thereby causing the polarized relay 100 to energize. Polarized relay 100, upon energizing, closes at armature 105 and its working contact a circuit for lighting the supervisory lamp SL as follows: from ground, working contact of armature 105 and said armature, low resistance Winding of relay 101, sleeve of jack J sleeve of plug P, spring 47, audits resting contact of the ringing key BK, resting contact of armature 48 and said armature to supervisory lamp 'SL and battery. The

lighting of the supervisory lamp SL indicates to the operator that the calling subscriber has hung up. The sleeve relay 101 in the trunk circuit TC is now held up over both its wind- 'ings in series; station through to the trunk conductors 111 The operator, upon perceiving the lighted condition of the supervisory lamp 'SL, re-

moves the plugs P and P from the jacks J and J respectively. In the trunk circuit TC relays 101 and 102 deenergize, thereby re storing said circuit to normal condition and in the train dispatchers trunk TR the sleeve relay 132 deenergizes thereby restoring the trunk circuit to normal.

Let us assume now that the train dispatcher for some reason desires a connection with a subscriber in the P. A. X. for instance the traflic manager. The dispatcher, in order to signal the operator, operates the key 139 which connects ground to the conductor 131. Responsive to this operation relay 133 energizes and closes a locking circuit for itself at armature 138 and at armature 137 closes a. circuit for lighting the call lamp L The operator, upon seeing the lighted condition of the lamp L inserts the plug P into the jack J 3 thereby energizing the sleeve re lay 132 of the dispatchers trunk TR as previously described Relay 132, uponenergizing, at armature 134 opens the circuit of the lamp L at armature 135 and its resting contact, opens the locking circuit of relay 133 and at its working contact prepares a circuit for flashing the supervisor I lamp SL; and at armature 136 and its working contact closes a bridge which includes the right-hand windings of the repeating coil across the dispatchers trunk conductors 130 and 132. By the operation of the listening-key LK the operator connects her head-set across the lefthand windings of the repeatingcoil of the trunk TR.

The operator, upon ascertaining that a dispatcher desires to be connected with the substation A, releases her listening key LK and The sleeve relay 101 of the trunk circuit TC is inserts the plug P into the jack J energized in the manner previously described.

Relay 101, upon energizing, closes a bridgeacross the conductors 111 and 112 thereby causing the operation of the lineswitch LS. The line relay of the lineswitch LS and the polarized relay 100 operate in series, the polarized relay at armature 105 closes a circuit through the lower winding of relay 101 for lighting the supervisory lamp SL.

The operator now operates the dial key DK and pulls her calling device oft normal preparatory to calling the number 01": the desired subscriber. WVhen the calling device CD is moved ofi normal, the shunt springs 64 are closed thereby energizing relay 61. Relay 61 upon energizing, at armature 62 opens the circuit of the operators head piece and at armature 63 closes a shunt circuit for deenergizing relay 101 of the trunk circuit TC as follows: from ground by way of working contact of armature 63 and said armature, conductor 65, working contact of spring 5:2 and said spring of dial key DK, resting contact and spring 47 and said spring of ringirn key BK, sleeve of plug P. sleeve of jack J, upper winding of relay 101 to ground at armature 108. Relay 101, upon dcenergizing, at armatures 106 and 107 closes a dialing circuit which cuts out-the repeating coil in the trunk circuit.

The lineswitch LS very quickly seizes an idle connector and when the calling device CD of the operators head-set O is returning to its normal position impulses are transmittcd for operating the connector switch to connect with the line of the desired subscriber. A portion of the dialing circuit may be traced as follows: conductor 111, normally closed springs controlled by armature 106, tip conductor of jack J tip of plug P, spring and its resting contact of ring key BK, working contact of spring 50 and said spring of dial key DK, conductor (36, impulse sprin of the calling device CD, operators induction coil, conductor 67. spring 51 and its working contact of the dial key DK, resting contact of spring 46 and said spring of ring key RK. ring conductor of plug P, ring spring of jack J normally closed springs controlled by armature 107, working contact of armature 110 and said armature to conductor 112, The impulses sent out by the operator "ause the connector switch to seize the bank contacts 17, 18 and 19 or multiples thereof in known manner.

Responsive to the seizure of the connector bank contacts 17, 18 and 19, the switching relay of the connector and the cut-otl' relay of the lineswitch LS energize in series. By the operation of the cut-off relay of the lineswitch LS, the lineswitch is prevented from operating and by the operation of the switching relay in the connector, ringing current is applied to conductors 9 and 10 for ringing the bell of the called station A. When the called subscriber answers, a relay operation takes place in the connector which cuts of? the ringing currentaud which also reverses battery lo the trunk conductors 11]. and 112 of the trunk circuit TC. Responsive to the re- \'er:.-'al.o'l' battery over the trunk conductors 111 and 112, polarized relay 100 deenergizes and opens the circuit of the supervisory lamp SL at armature 105. By the extinguishing oi supervisory lamp SL the operator is notified that the called subscriber has answered the call. The called subscriber and the dispatcher may now converse with each other as desired.

It for some reason the dispatcher wishes to recall the operator. the dispatcher operates the key 139 thereby causing the energization of relay 133. Relay. 133, upon energizing,

mature 138 and said armature, armature 135 and its working contact, upper low resistance winding of relay 132, sleeve of pick J sleeve of plug P. resting contact of spring 58 of the ringing key BK, to supervisory lamp SL' and battery. The operator upon perceiving the lighted condition of the supervisory lamp .SL operates either her listening key LK or dial key DK thereby connecting her headset across the talking conductors of the trunk TR.

lVhen the trafilc manager of substation A and the dispatcher have finished conversation the trailic manager hangs up his receiver thereby causing a relay operation in the connector to reverse the flow of current back to normal. Responsive to the reversal of the current flow to normal in the conductors 111 and 112. the polarized relay 100 energizes and again closes the circuit for the supervisory lamp SL at armature 105. The operator, upon seeing the lighted condition of the supervisory lamp SL, removes the cord circuit CC from the jacks J and J thereby restoring the trunk circuit TC and the dispatchers trunk TR to normal as previously described.

Toll calls between the automatic subscribers, dispatchers trunks or other toll lines are handled with the aid of the cord circuit CO in the same manner as the previously described connections. It may well he mentioned at this time that the relays 43 and 44 in the cord circuit CC are used for supervisory purposes. such as ring-down supervision on the toll lines.

Private automatic subscribers of one P. A. X. may call subscribers in the other P. A. X. over direct trunks between the two P. A. Xfs. In order to an automatic subscriber in one exchange to call an automatic subscriber in the other exchange the calling subsciiber must dial the digit 9 to automatically trunk the call over the ninth level of the selector connectors through to the other P. A. X. and then dial the number of the desired subscrihefis station. The method of setting up automatic calls of this nature and local calls in. P. A. being well known in the art, it is considered unnecessary to descrihc such connections in detail.

Having described the telephone connections which ordinarily take place in connection with the privately owned telephone systems of the railroad company, a description will now be given of the various circuits which permit an operator to give man ual service to important lines which are in trouble.

A subscribers line may become grounded on one side of the line, either the negative line conductor or the positive line conductor,

or a line may become grounded 011 both line conductors with a leak to ground of about 650 ohms on one of'the conductors, or a line may become, partially shorted through a resistance of about 1,000 ohms without seriously interfering with conversation. WVhile it is possible to carryonconversation over lines having the above trouble conditions, the trouble may be sufficient to'render dialing partially or completely ineffective to proper- 1y operate the automatic switches in the on change.

In order to describe the next phase of the invention it will be assumed that the railroad traflic managers line, station A, is in trouble and that he is unable to complete automatic connections. If the trouble on the line of station A cannot be immediately fixed, the hospital trunk plug HTP is inserted into the line protectors on the main frame thereby connecting the line conductors 1 and 2 with the trunk conductors 21 and 22, and the conductors 9 and 10 with the trunk conductors 35 and 36. Theplug HTP is designed so that either trunk conductor 21 or 22 can be connected to either line conductor 1 or 2.

It will now be assumed that the traillc manager at substation A. desires to be connected with the train dispatcher DIS. Re

' sponsiveto the removal of the receiver at substation A, hne relay 24 energizes over the conductors 21 and 22 and the calling subscribers loop. It may well be mentioned at this time that the line relay 24 is especially designed so as to operate only responsive to the removal of the receiver by the calling party and not to operate under adverse con ditions such as is encountered when subscriberslines are in trouble. The non-i11- ductive resistances connected to the line relay 24 regulate the flow of transmission cur rent to the transmitter and receiver of the calling station and, in addition, the number of turns around the core of relay 24 has been greatly reduced so as to reduce the efficiency of the line relay. That is, the line relay is designed and Wound so that it is less sensitive than ordinary line relays and will not therefore pull up or energize when there is a slight short circuit on the line or when one of the conductors becomes grounded. Relay 24, upon energizing, at armature 28.closes a circuit for lighting the call lamp L and at armature 30 opens a point in the supervisory circuit which will be explained hereinafter.

The operator, upon perceiving the lighted condition of the call lamp L, inserts the plug P of the cord circuit CC into the jack J. Responsive to the insertion of the plug P into the jack J, sleeve relay 25 energizes over the following circuit: from ground by way of the normally closed springs controlled by armature 33, lower winding of relay 25, sleeve of jack J, and sleeve of plug P over the circuit previously traced to battery at the supervisory lamp SL. Relay 25, upon energizing, at armature 31 opens the circuit of the call lamp L thereby extinguishing the same; at armature 32 opens the circuit of relay 23; and at armature 33 opens the original energizing circuit of relay 25 and substitutes the ground through the resistance for maintaining relay 25 energized.

The operator, upon ascertaining that the station A desires to be connected with the dis patchers trunk TR, inserts the plug P into the jack J 3 and completes the connection in the same manner as previously described.

After termination of conversation and responsive to the replacement of the receiver at the calling station A, line relay 24 deenergizes and at armature 30 closes a circuit through the low resistance for lighting the supervisory lamp SL as follows from ground by way of working contact of armature 33 and said armature, upper low resistance winding of relay 25, armature 30 and its resting contact, sleeve of jackJ, sleeve of plug P, and over the previously traced circuit to supervisory lamp SL and battery. It will be noted that ground from armature 29 through the lower winding of relay 25 and ground through armature 33 and the upper winding are connected in multiple thereby maintaining relay25 in operated position.

The operator, upon observing the lighted condition of the supervisory lamp SL, removes her plugs P and P from the jacks J and J respectively. The sleeve relay 25 now deenergizes and the hospital trunk HT is now in normal position.

Assuming now that due to a certain condition on the subscribers line the line relay 24 will not release when the calling subscriber replaces his receiver, under these conditions the supervisory lamp SL ofcourse will not be lighted when the calling subscriber replaces his receiver and the operator will therefore after a certain period of time operate her listening key in order to observe whether or not the calling party has hung up.- In case the operator finds that the calling party has replaced his receiver she will then'operate the dial key DK and move her calling device CD ofi normal. Responsive to the operation of the calling device CD, relay 61 energizes as before described and connects ground at armature 63 to conductor 65. Ground on conductor 65 now extends through the springs on the dial and ring keys to thewinding of relay 25 allowing said relay to de-- energize. Relay 25, upon deenergizing closes at armature 32 a circult for energizing. relay 23. Relay 23, upon energizing, opens the circuit of theline relay 24 at armatures 26 and 27, thereby allowing said relay to release. ,After ground is removed from the conductor due to the deenergization of relay 61, the sleeve relay 25 is again energized. The

ope 'ator is notified :by the extinguishing of the lamp L that the line relay has been .released. The equipment is now returned to normal by the removal of the plug P from the j a ck J.

It will be noted that by the operation of the :alling device in the substation A the resistance of the transmitter and receiver is shunted by the shunt springs thereby permitting a greater range under trouble conditions over which the line relay 2% canbe effective- 1y operated.

Having described the method of manually extending calls from a subscribers line which is in trouble, a description will nowbe given of the method of intercepting calls to asubscriber whose line is in trouble.

It will now be assumed that a local subscriber in the same exchange as the station A has extended a connection 'to a connector and that the connector has-seized the connector bank terminals 17, 18, and 19 which are assigned to the station A. The switching relay of theconnector now energizes in series with the cut-off relay ofthe lineswitch LS thereby preventing the hunting operation of thelineswitch LS in known manner. Responsive to the energization of the switching relay in the connector, ringing current is applied to conductors 9 and 1.0. The ringing current flows over the trunk conductors 35 and'36 thereby operating the ring-up relay 38. The ring-up relay 38 and the sleeve relay 39 are mechanically the same as the ring-up andcut-off relays disclosed inthe before mentioned Erickson patent. Ring-up relay 38, upon energizing, mechanically locks itself in operated position and closes a circuit for lighting the call lamp L.

The operator, upon observing the lighted condition of lamp L, inserts the plug P of the cord oircuit'CC int-othe jack J. Responsive to the insertion of the plug P into the jack J, the sleeve relay "39 of the hospital trunk HT energizes as follows: ground throughthe lower high resistance winding of relay 39, sleeve of jack J, sleeve of plug P,

resting contact of spring 58 and said spring to supervisory lamp SL and battery. The supervisory lamp SL is not lighted over this circuit on account of the high resistance of relay 39.

The operator can either converse with the calling subscriber by operating her listening key LK or can immediately insert the plug I? into the jack J without talking to the calling subscriber because the operator knows that thesnbscriber has attempted to automatically call the station A and thereforeshe could complete the connection without conversing with the calling subscriber. Responsive to the insertion of the plug P into thejack J the sleeve relay 25 of the hospital ringing key RK thereby opening at spring t7 the circuit of the sleeve relay .25. The

sleeve relay 25 deenergizes responsive to the opening of the spring 47 of the ringing key RK because the high resistance as does not permit suflicient current llow to flow through the winding of relay 25 to maintain the same energized. Relay :25 upon deenergizing, closes at armature 3:2 a circuit t'or energizing relay 23. Relay 23 at armaturcs 26 and 27 disconnects the line relay Q-l and shunts out the condensers in the trunk circuit so that the ringing current will not pass through the condensers. Ringing currentnow flows from springs 45 and 4-6 oi the ringing key over the talking conductors of the cord and hospital trunk for ringing the bell of the called subscriber. The operator, upon restoring the ringing key BK, again closes the circuit for relay 25 which energizes and opens the circuit of relay 23. Relay 23 at armaturcs 26 and 27 connects the line relay 24 across the conductors 21 and 22 so that the line relay will be energized over the called sub;-:cril'iers loop when the called subscriber answers. Relay 24, upon energizing, at armature :20 opens the original energizing circuit and sub stitutes a ground through resistance for maintaining relay 25 energized; and at armature 30 opens a point in the supervisory circuit. On termination of conversation, the called subscriber hangs up and releases line relay 24- thereby again closing the supervisory circuit at armature 30 for lighting the supervisory lamp SL as previously described. The operator now removes the plugs P and P from jacks J and J thereby restoringthe apparatus to normal.

The hospital trunk HT is designed so that if the occasion arises, the operator may use this trunk circuit as an outgoing trunk to complete calls to the P. A. X. When the operator desires to use the hospital trunk HT as an outgoing trunk she will insert the plug P into jack J thereby energizing sleeve relay 39 over a circuit as follows: ground through the lower winding of sleeve relay 39. sleeve of jack J, sleeve of plug P to battery throu 1h resistances 59 and 60 and to battery through lamp SL. Responsive to the energizalion of relay 39 a bridge including the polarized relay 37 is closed across the trunk conductors 36 and 35 at armature 42 and its working contact. The closure of this bridge causes the operation of the lineswitcli to hunt for an idle connector. By the operation of dial key *DK a bridge including the operatofis head set and calling device CD is closed in shunt ot the bridge including the polarized relay 37. \Vhen the calling device Cl) is moved off normal relay (51 is energized by way of shunt springs 64 and said relay at armature 63 connects ground to conductor Hill Ill)

iof the connector.

claims. r

65. Sleeve relay 39 is shunted by this ground and therefore releases during the dialling operation. By the deenergization of relay 39 the bridge including the polarized relay 37 is opened so that the impulses generated by the calling deviceCD on its return to normal are effective to operate the connector switch. The impulsing circuit extends through the cord circuit CC in the manner previously described to'the tip and ring conductors and to the conductors 35 and 36 and 'from these by way of conductors 9 and 10,

lineswitch wipers and 16 to the line relay The impulses now operate the connector to the line of the desired subscriber. The polarized relay 37 energizes in series with the normal flow of current over conductors and 36 thereby closing at ar mature a circuit through the low resistance winding ofsleeve relay 39 for lighting a supervisory lamp SL. lVhen the called subscriber answers a relay operation takes place'in the connector which reverses the flow of current over conductors 36 and 35 thereby causing the deenergization of polar relay 37 Polar relay 37 thereby opens the circuit of the supervisory lamp SL notifying the operator that the called subscriber has answered. When the called subscriber replaces his receiver after termination of conversation, a relay operation in the connector takes place which reverses the flow of current over conductors 36 and 25 to normal thereby again energizing polar relay 3?.

lamp SL notifying theoperator that the called party has replaced his receiver. The release of the connection isnow the same previously described.

Having described the invention, its utility and operation. whatis considered new and is desired to have protected by Letters Patent will be set forth in the appended What is claimed is 1. In a telephone system, two exchanges, a subscribers line, a pair of hospital trunks terminating in one exchange in separatejacks, a plug common to said trunks for terminating. said trunks at the other exchange and for connecting said trunks with the incoming and outgoing sections of said line,

. respectively, whensaid line is in trouble, and

means at said first mentioned exchange for completing calls to and from said line over said trunks.

2. In a, telephone system, a subscribers line, means including automatic switches normally controllable by subscribers on said line to complete connections to .called lines, a pair of hospital trunks terminating in one end in separate jacks and in the other end in a plug common to said trunks, said plug adapted when connected to said line to remove the control of said switches from said line, to connect the subscribers line conductors to one of said trunks, and to connect the exchange conductors over which the automatic switches are normally controlled by subscribers on said line to the other of said trunks, and a cord circuit adapted to be con nected to both said trunks to complete a call to said line.

3. In a telephone system, an automatic exchan e, a manual exchange, a main frame in saic automatic exchange, subscribers line conductors terminating on said main frame, a line switch and connector bank terminals in said automatic exchange, exchange conductors normally connecting said line con ductors with said lineswitch and terminals, means at said main frame adaptable for use when said line is in trouble for disconnecting said line conductorsfrom said exchange conductors and for extending said line and exchange conductors to a switchboard in, said manual office, said extended line conductors terminating at said switchboard in line equip-- ment and ack, said extended exchange conductors terminating at said switchboard in trunk equipment and a second jack, and means at said switchboard for connecting said line conductors with said exchange conductors. I

4. In a telephone system, a subscribers line, means including automatic switches controllable by subscribers on said line to complete connections to called lines, means for removing the control of said automatic switches from a subscribers line in trouble, trunk equipment for terminating said line in a manual switchboard, and a line relay in said trunk equipment having two windings of only a few turns around the core of said relay and having a non-inductive resistance connected to each winding for regulating the flow of talking and operating current to said line whereby said relay is operative responsive only to the removal of the receiver on said line andnot responsive tothe trouble conditions on said line. k V

5. In a telephone system, a subscribers line, means including automatic switches controllable by subscribers on said line to complete connections to called lines, means for removing the control of said automatic switches from a subscribers line in trouble, trunk equipment for terminating said line in a manual switchboard, a line relay in said trunk equipment having two windings of only a few turns around the core of said relay and having a non-inductive resistance connected to each winding for regulating the flow of talking and operating current to said line whereby said relay is operative responsive only to the removal of the receiver on said line and not responsive to the trouble conditions on said line, said trouble conditions maintaining said relay in operated position after the subscriber has replaced his receiver,

and means for automatically restoring said relay to normal position.

6. In a telephone system, a subscrihers line, line equipment for said line for use in case said line is in trouble, a line relay in said equipment energized only responsive to the removal of the receiver of said line, said re lay being maintained in bridge of the line duringconversation to feed talking current to the line, and circuit arrangements in said equipment for restoring said relay to normal position after the receiver is replaced in case trouble conditions on said line maintain the relay energized.

7 In a telephone system, a sabscribefis line, line equipment for said line for use in case said line is in trouble, a line relay in said equipment; energized only responsive to the removal of the receiver of said line, said relay being maintained in bridge of the line during conversation to feed talking current to the line, an operators calling device, and means operative responsive to the operation of said calling device for restoring said relay to normal position after the receiver is replaced in case trouble conditions on said line maintain the relay energized.

S. In a telephone system, a relay having two windings, contacts on said relay, a supervisory lamp. a circuit for energizing said relay including only one winding of said. relay and said lamp in series, and a circuit for lighting said lamp including the other winding of said relay and said contacts and for maintaining said relay energized over its two windings in parallel.

S). In a telephone system. a relay having two windings, contacts on said rel ay, a supervisory lam a circuit for energizing said relay including said contacts, only one of said windings, and said lamp in series, and a circuit for lighting said lamp including the other winding of said relay, said relay being maintained energized over its two windings in parallel.

10. In a telephone system, a subscribers line, a pair of hospital trunks terminating in one end in separate jacks, a plug common to said trunks for terminating said trunks at the other end, and a cord circuit adapted to complete a connection to said line through the medium of said plug when the line is called, said connection including the first of said trunks, said cord circuit, and the second of said trunks in series in the order named.

11. In a telephone system, a subscribers line, other subscribers lines, an operators switchboard, a pair of hospital trunks terminating in separate jacks at said switchboard, a plug for connecting said trucks with the incoiniin and outgoing sections of said line, respectively, when said line is in trouble, and means for completing outgoing calls from said switchboard over the hospital trunk connected to said incoming section of said line to said other subscribers lines.

12. In a telephone system. an automatic exchange, a main frame in said exchange, subscribers line conductors extending from the subscribers telephone set and terminating in said main frame, a lineswitch and connector bank terminals individual to said line in said exchange, exchange conductors extending from said main frame and normally connecting said line conductors with said lineswitch and terminals, an operators switchboard, a hospital trunk at said main frame for dis connecting said line conductors from said exchange conductors and for extending said conductors to said switchboard when said line is; in trouble, other subscribers lines, and operator controlled means for completing connections between said other subscribers lines over said hospital trunk.

13. In a telephone system, an automatic exchange, a main frame in said exchange, subscrihers line conductors extending from the subscribers telephone set and terminating in said main frame, a lineswitch and connector bank terminals individual to said line in said exchange, exchange conductors ex tending from said main frame and normally connecting said line conductors with said lineswitch and terminals, an operatoi"s switchboard, a hospital trunk at said main frame for disconnecting said line conductors from said exchange conductors and for extending said conductors to said switchboard when said line is in trouble, and means for completing outgoing calls from said switchboard over said hospital trunk.

In witness whereof, I hereunto subscribe my name this 29th day of November, A. 1)., 1926.

ROY F. GOULD. 

